Method for controlling a cooking point of a gas oven and device

ABSTRACT

In one embodiment, a method for operating a cooking point with a gas burner of a gas hob is disclosed in which pan detection is provided for switching off the gas burner when the pan is removed, wherein the pan detection unit can detect the re-placement of a removed pan onto the cooking point and then cause a further operation of the gas burner by igniting the gas burner. When the gas burner is ignited after re-placement of the pan, a power level originally set for the gas burner is only achieved after a time delay, thereby preventing any injury to the user.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Application Number 10 2009014 570.2, filed on Mar. 17, 2009, the contents of which areincorporated by reference for all that it teaches.

FIELD OF THE INVENTION

The invention relates to a method for operating a gas burner at acooking point, as used in a gas hob. Similarly, the invention relates toa corresponding device.

BACKGROUND OF THE INVENTION

There are known hobs with pan detection at a cooking point, the pandetection detecting whether a pan has been placed on or removed. Withthe removal of the pan, the cooking point is switched off, but a powerlevel (i.e., gas output level) that has been set continues to bemaintained. If a pan is then placed on again, the burner ignitesimmediately and, on account of the pressure conditions in the gas systemand the delay of the igniting process, a briefly larger gas flame mayoccur, even reaching to beyond the handles of the pan. The gas flamewill at least be of the size of the level that has been set, possiblyeven larger because of the briefly larger flame. The user must thereforequickly remove his/her hands from the handles of the pan in order not tobe burned by the flame.

One aspect of the invention addresses the problem of providing a methodmentioned at the beginning and a corresponding device by whichdisadvantages of the prior art can be overcome and, in particular,provides more convenient operation of a cooking point with a gas burnerwith reduced risk of injury.

SUMMARY

This problem is solved by a method and device with the features asclaimed herein. Advantageous and preferred refinements of the inventionare the subject of the further claims and are explained in more detailbelow. The wording of the claims is incorporated in the description byexpress reference.

It is provided that, as described above, at the cooking point there is apan detection, by means of which the gas burner is switched off or acorresponding gas valve on the gas burner is closed when the pan isremoved or when the pan detection establishes this. For this purpose,the pan detection may advantageously be formed in the customary way thatis known in principle, with capacitive, optical or mechanical systemsbeing suitable in particular. Furthermore, the pan detection togetherwith a control of the cooking point or the gas burner or the gas valvethereof, in particular together with an ignition device for the flame,brings about the effect that the pan detection detects when a pan thathas previously been removed is re-placed onto the cooking point. It thenreactivates the gas burner by igniting the gas burner and/or opening thegas valve, in order that the cooking process is therefore continued asit were of its own accord after the pan is placed on again.

According to one aspect of the invention, when the gas burner isignited, that is to say when the pan has been placed on again, theoriginally set operation of the gas burner or a power level originallyset for the gas burner, only takes place or is reached to the fullextent after a certain time delay. A user therefore then has time, atleast the time of this delay, to remove his/her hands from the panagain, and in this way the risk of burning is reduced or eliminated.

Said delay may advantageously be a few seconds, for example half asecond to three or even five seconds. For instance, one to two secondshave proven to be advantageous, in order indeed to allow sufficient timeon the one hand for the hands to be removed from the pan and on theother hand for a user to see relatively quickly that the cooking pointis in operation again, or in turn in order that the cooking process isalso not interrupted unnecessarily long.

According to a one embodiment of the invention, it is possible that thepan detection detects the re-placed pan immediately or only with minimaldelay, but the gas burner only ignites at all after said delay of a fewseconds. This therefore means that the ignition of the gas burner waitsfor a short time after detection of the re-placed pan in order that theuser can remove his/her hands from the pan. Only after the time delay isthe gas burner ignited again. This may take place with a lower powerlevel than that previously set or used. Since, however, a certain timeis already available to remove the hands from the pan, re-ignition ofthe gas burner after the delay may also take place right away with thefull power level previously set.

In another embodiment of the invention, the pan detection may likewisedetect the re-placement of the pan immediately or with minimal delay andalso ignite the gas burner immediately or as soon as possible. However,this ignition of the gas burner takes place with a power level which,though high enough that the gas burner reliably ignites, is at the sametime well below the power level previously set. This immediate ignitionadvantageously takes place with the lowest possible power level of thegas burner at which reliable ignition occurs. Then, however, the powerlevel is slowly increased, until the power level previously set isreached. This slow increase of the power level proceeds over theaforementioned time delay and may indeed take the few seconds mentioned.

In the case of this embodiment of the invention, the gas burner istherefore ignited immediately when the re-placed pan is detected andwhen a user, in all probability, still has his/her hands on the pan.Since, however, the power level used is not the full level previouslyset, which could possibly lead to burns, but only a lower or thesmallest possible level, the risk of burning is in turn reduced oreliminated. By the time the power level is increased to that previouslyset, the time delay has in turn elapsed and a user has sufficient timeto remove his/her hands. A gas flame with a very small or the smallestpossible power level will generally not be sufficient to cause burningof the hands holding the pan placed on.

In the case of this embodiment of the invention, the power level ispossibly increased continuously to the value of the power levelpreviously set. In further embodiments, it may first be increased slowlyand then to ever increasing degree or finally, also at the end of thedelay, be increased abruptly.

In another embodiment of the invention, it may be provided that theremoval of the pan from the cooking point is optically indicated. Forthis purpose, indicating means such as illuminating source or the like,for example light-emitting diodes, may be arranged in the region of thecooking point. Furthermore, an acoustic signal output may also takeplace. A signal output may continue for as long as the pan is removedand at the same time the cooking point has not yet been switched off asa result of a maximum time being exceeded.

In another embodiment of the invention, it may be provided that, after amaximum time is exceeded, possibly in the range between 3 minutes and 15minutes, advantageously between 5 minutes and 10 minutes, the readinessof the cooking point is cancelled. For this purpose, the power levelsetting is cancelled. Therefore, when a pan is placed on again, there isno automatic further operation of the cooking point or automaticswitching back on of the gas burner. It may be provided in this respectthat first an operating element for the power level setting has to beactuated, that is to say a power level setting has to be manually setagain. In this way, the control can reliably detect that a user is againin attendance. In particular, the power level first may be set againright back to zero and subsequently set to the desired degree. Also inthis respect it may be provided that such exceeding of the maximum timein the way prescribed is optically and/or acoustically indicated.

In another embodiment of the invention, an additional safety feature maybe provided that a signal is outputted shortly before the gas burner isre-ignited or shortly before the previously set power level is reached.This may be an optical signal or advantageously an acoustic signal. Sucha signal may, for example, be generated half a second or a second beforethe power level originally set is reached when the pan is placed onagain and the gas burner is automatically ignited.

In another embodiment of the invention, when the cooking point isswitched off or the gas burner is turned off, in particular when aplaced-on pan is removed, a slow turning-off operation takes place, orthe power level is as it were slowly brought to zero. This may last anumber of seconds, for example two seconds to five seconds. Furthermore,it may at the same time be indicated, once again optically and/oracoustically in the aforementioned way. In particular, such slow turningoff may also mean that, after the pan is removed, said few seconds arewaited before the power level is brought down or the gas burner isturned off. As a result, the gas burner is not switched off unwantedly,which can result due to a malfunctions or the like when a pan is brieflynot detected as placed-on.

A control in which both the pan detection and the control for the gasvalve of the gas burner are integrated together with measurement of thetime or the delay may possibly be provided in a central control of acorresponding gas hob. Alternatively, it may be designed as anadditional control for certain cooking points.

The output of a signal, in particular an acoustic signal, before theignition of the gas burner may have the advantage of detecting an objectother than a pan has been placed on, for example a cooking spoon or thelike, and warning an operator of the imminent ignition of the gasburner. Then, the object inadvertently placed on can be removed againthus avoiding an accident.

These and further features are evident not only from the claims, butalso from the description and the drawings, where the individualfeatures can be realized in each case by themselves or as a plurality inthe form of sub-combinations in an embodiment of the invention and inother fields and can constitute advantageous and inherently protectableembodiments for which protection is claimed here. The subdivision of theapplication into individual sections and subheadings do not restrict thegeneral validity of the statements made thereunder.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated schematically inthe drawings and are explained in greater detail below. In the drawings:

FIG. 1 shows a side view of a gas hob according to one embodiment of theinvention with a device for the time-delayed ignition of a gas burner ofa cooking point and

FIG. 2 shows a diagram of one embodiment of the power progression overtime for various ways of increasing the power.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 illustrates a gas hob 11 as a device according to the invention,on which the method according to the invention can be carried out. Thegas hob 11 has a conventional hob panel 12, and a cooking point 14thereof is illustrated. The cooking point 14 has a conventional gasburner 16 with a gas valve 17 arranged under the hob panel 12, fromwhich valve said burner is supplied. Provided at the gas burner 16 is anignition device 18 and advantageously a monitoring device (notillustrated) for the gas flames 19. An essentially conventional pansupport 20, on which a pan 22 is placed over the gas burner 16 and thecooking point 14, is also provided. This pan support has yet furtherfunctions, as still to be explained below. As usual, the pan has sidehandles 23, which are being gripped by hands 24 of the user, for examplebecause said user has just placed the pan 22 on again.

Provided on the gas hob 11 is a controller 26, which is connected notonly to the gas valve 17, for the activation thereof, and to theignition device 18 but also, though not of any consequence here, to apossible flame monitor. Furthermore, the controller 26 is connected to apan detection device, which is not described in any more detail but isformed as a known reflex light barrier and is arranged underneath thehob panel 12. Furthermore, the controller 26 is connected to signaltransmitters under the hob panel 12, such as an acoustic signaltransmitter 28 a and an optical signal transmitter 28 b. It is alsopossible to omit the signal transmitters or to provide only one of thetwo.

When the pan 22 is removed from the cooking point 14, as the thick arrowindicates, the pan detection device 21 together with the controller 26detects this. The latter then closes the gas valve 17, so that the gasburner 16 goes out or the gas flames 19 are extinguished. If the pan 22is then placed on again with the hands 24 on the handles 23, the pandetection device 21 detects the pan 22. This then corresponds to thepoint in time t₀ in the diagram of the power P over the time t accordingto FIG. 2, to be specific when the power of the gas burner 16 isincreased from zero, that is when the gas valve 17 is closed. Here theremay be an abrupt increase according to the solid line to a powerP_(min), which is chosen such that it is the minimum power or minimumpower level or minimum amount of gas with which the gas burner 16 canignite and burn. Up until the point in time t₁, which is reached after adelay time T_(V), which is the delay time mentioned at the beginning,there may be a few seconds, advantageously one to two seconds. Over thisdelay time T_(V), the power P is then not increased over the minimumpower P_(min), as shown by the solid line. This only happens abruptly atthe point in time t₁, and then specifically to the power originally setP₀. This power P₀ was the power before the pan 22 was removed. Duringthe delay time T_(V), an operator therefore has sufficient time afterplacing the pan 22 onto the cooking point 14, that is the said one totwo seconds, to remove the hands 24 again from the region in which thegas flames 19 can come. Although the gas burner 16 ignites again, thegas flames 19 scarcely reach over the base of the pan 22 to the sidesand up to the handles 23 or the hands 24, since said burner operateswith the lowest possible minimum power.

As an alternative to keeping to the minimum power P_(min) along with anabrupt increase, the power may, as from the point in time t₀, firstincrease slightly and then ever more quickly as shown by a dotted curvein the manner of a parabola or non-linearly. As a result, it can also atthe same time be signalled to a user that not only has re-ignition takenplace but there has also been an increase in the power automaticallybeyond the minimum power P_(min). The user therefore does not have toworry that the cooking point 14 is malfunctioning.

In another alternative embodiment, the increase in output level as fromthe point in time t_(o) may take place uniformly as shown by thedash-dotted representation. Although an increase in the burning poweronce again takes place here somewhat more quickly than in the case ofthe two previous curves, it is still always in such a way that, forexample after the elapse of a time T_(V)/2 after the point in time t₀,there is still a much lower power than the power previously set P₀.

In yet a further alternative refinement of the method, at the point intime t₀, the gas burner 16 is still out or the gas valve 17 is closed.Only at the point in time t₁, that is after the delay time T_(V), is thegas burner 16 ignited by opening of the gas valve 17 and actuation ofthe ignition device 18, then however right away as shown by the dashedcurve with the full pre-set power P₀. This has the advantage that even apossibly existing risk of burning caused by a gas flame with the lowminimum power P_(min) is eliminated, since indeed there are still no gasflames 19. At the same time, it must then be noted however that there-ignition of the gas burner 16 at the point in time t₁ then takesplace with the full pre-set power P₀ and abruptly.

As explained previously, an acoustic and/or optical signal output by thesignal transmitters 28 a and 28 b may take place at a point in time t₀,t₁ or a point in time in between. This may signal re-ignition of the gasburner 16, that the full power previously set P₀ will soon be reached orhas been reached, or something similar.

1. A method for operating a cooking point with a gas burner of a gas hobcomprising: switching off the gas burner by a pan detection unit byswitching off the gas burner by closing a corresponding gas valve when apan is detected initially at the cooking point and then detected asbeing removed at the cooking point; detecting by the pan detection unitwhen a removed pan is re-placed onto the cooking point; and causing arenewed operation of the gas burner by igniting the gas burner byopening the gas valve, wherein, when the gas burner is ignited after thepan is placed on said cooking point again, wherein the set power leveloriginally set for the gas burner only takes place to the full extentwith a delay.
 2. The method as claimed in claim 1, wherein the delay ishalf a second to five seconds.
 3. The method as claimed in claim 1,wherein the pan detection unit detects immediately when said pan isplaced on again and only re-ignites the gas burner again after the timedelay.
 4. The method as claimed in claim 3, wherein said re-ignition ofthe gas burner after the delay takes place with the power levelpreviously set.
 5. The method as claimed in claim 1, wherein the gasburner is ignited immediately when said pan is placed on again, orimmediately after detection of said pan occurs by the pan detectionunit, with a power level which lies below the power level previouslyset, the power level then being increased up to the power levelpreviously set over the time period of the delay.
 6. The method asclaimed in claim 5, wherein the gas burner is ignited with a power levelin the range of the minimum power required for the ignition of the gasburner and followed by increasing the power level of the gas burner. 7.The method as claimed in claim 1, wherein removal of the pan from thecooking point is optically indicated.
 8. The method as claimed in claim7, wherein the removal of the pan is optically indicated by anillumination source.
 9. The method as claimed in claim 1, wherein asignal is output shortly before re-ignition of the gas burner.
 10. Themethod as claimed in claim 1, wherein the signal is an acoustic signal.11. The method as claimed in claim 1, wherein, after a maximum time isexceeded, the power level setting is cancelled and operation of thecooking point when the pan is replaced does not take place automaticallybut wherein a power level is manually set.
 12. The method as claimed inclaim 11, wherein the power level is set by manually resetting the powerlevel to zero and subsequently increasing the power.
 13. The method asclaimed in claim 11, wherein the maximum time is three minutes tofifteen minutes.
 14. The method as claimed in claim 1, wherein slowturning-off with a turning-off time of a few seconds is provided forswitching off the cooking point by turning off the gas burner.
 15. Themethod as claimed in claim 14, wherein the turning off takes place withone or more of an optical or acoustic indication taking place at thesame time.
 16. An apparatus for operating a cooking point of a gasburner of a gas hob comprising: a pan detection unit for detecting thepresence of a pan on said cooking point; a gas valve configured tocontrol the flow of gas provided to said gas burner of said cookingpoint; and a controller configured to receive a first signal from saidpan detection unit indicating the presence of said pan, said controllerconfigured to close said gas valve from a set value when removal of saidpan is determined from a second signal received from said pan detectionunit, said controller configured to open said gas valve when a thirdsignal is received from said pan detection unit indicating replacementof said pan onto the cooking point, wherein said gas valve is opened tosaid set value after a time delay.